Regex Tester
Test a JavaScript regular expression against your own text and see every match highlighted, with capture groups broken out.
How to use the Regex Tester
- Type a pattern (without the surrounding slashes).
- Toggle flags: g (global), i (case-insensitive), m (multiline), s (dot matches newline).
- Paste your test text — matches and any capture groups appear below as you type.
How it works
This tests patterns using JavaScript's native RegExp engine — the same one your browser's console uses — so results match exactly what you'd get in JS code. For example, the pattern \d+ with the g flag against "Room 42, Floor 7" finds two matches: "42" and "7". If your pattern has capture groups — parentheses like (\d{3})-(\d{4}) — each match's captured pieces are listed separately underneath it.
Frequently asked questions
Does this test PCRE, Python, or another regex flavor?
No — only JavaScript's regex syntax. Most common patterns work the same across languages, but some features (like Python's named groups syntax) differ.
Is my text sent anywhere?
No — matching runs entirely in your browser using JavaScript's built-in RegExp, nothing is uploaded.
Why did my browser freeze on a complex pattern?
Certain regex patterns (heavy nested quantifiers, like (a+)+b against a long non-matching string) can cause "catastrophic backtracking," which is slow in any regex engine, not specific to this tool. If a pattern hangs, refresh the page and simplify it.